Labelling machine are used to apply labels to articles of all sorts, particularly to containers for many liquid or powder products including not only food products such as milk, fruit juices or beverages in general, but also mineral lubricating or detergent oils.
Very briefly, labelling machines of the known type comprise a storage for labels to be applied onto respective containers, a unit for applying the glue onto the label and for conveying label with glue thereon towards respective containers, and a gluing group for cold-gluing the labels onto respective containers.
In greater detail, the unit comprises:                a roll covered with glue and rotating about a first axis;        a first carousel which rotates about a second axis and comprises a plurality of paddles adapted to subsequently cooperate with the roll so as to be covered with glue and to pick relative labels from the storage; and        a second carousel which rotates about a third axis, and comprises a plurality of hooks which receive respective labels with glue thereon from first carousel and convey respective labels towards respective containers.        
The first carousel is driven in rotation in a first direction by a motor while the roll and the second carousel are driven in rotation by the first carousel in a second direction which is opposite to the first direction.
Alternatively, the second carousel may be driven in rotation by a further motor.
More precisely, the motor drives in rotation a first gear which engages with two gear trains operatively connected respectively to the roll and to the second carousel.
Each gear train comprises a plurality of gears in order to ensure a proper reduction ratio between the angular speed of the first carousel and the angular speed of the roll and of the second carousel.
Furthermore, each gear train must perforce comprise at least an idler gear in order to ensure that the roll and the second carousel rotate in the second direction.
A need is felt in the industry to reduce the number of components necessary to transmit the motion between the first carousel and the second carousel, and between the first carousel and the roll, so as to reduce manufacturing costs, maintenance costs and the overall noise of the unit.
Furthermore, a need is felt in the industry to manufacture an unit which may easily and economically realize different positions of the roll and of the second carousel with respect to the first carousel.
Finally, each kind of labelling machine has a specific pitch between the containers and a specific number of hooks. On the contrary, the number of paddles is generally constant.
Therefore, the transmission ratio between the first and the second carousel depends on the pitch between the containers.
A need is felt in the industry to economically change the transmission ratio between the first and the second carousel.
It is an object of the present invention to provide a unit for applying glue on labels to be cold-glued onto relative containers and for conveying such labels applied with glue designed to meet at least one of the above-identified requirements in a straightforward, low-cost manner.
According to the present invention, there is provided a unit for applying glue on labels to be cold-applied onto relative containers and for conveying such labels applied with glue as claimed in claim 1.